Control apparatus



'Nov. 5; 1946.

CONTROL APPARATUS Filed Jan. 26, 1943 T. A@ COHEN y 2,410,568

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Patented Nov. 5, 1946 CONTROL APPARATUS Theodore A. Cohen, Chicago, Ill., assignor, by

mesne assignments, to Wheelco Instruments j Company, Chicago, Ill., a corporation o f Illinois Application January 26, 1943, Serial No. 474,041

1i claims.y (01.122-448) a dangerous level notwithstanding the normal provision for automatically maintaining the liquid level by controlling the liquid supply. In this connection it is highlydesirable to provide such a dual control-for safeguarding the boiler wherein duplication of parts is minimized, consistent with maintaining the safeguarding character of the component parts of such dual control, Whereinthe burner will be shut down in event of failure of the water supply, and wherein the dual control is accomplished sharply, effectively and efciently.

Other and further objects of this invention will be apparent as the same becomes better understood from an examination of the specification and claims in conjunction with the accompanying drawing -whereinz Figure 1 is a schematic and diagrammatic view of an apparatus embodying my invention;

Figure 2 is a graphic illustration of the characteristics of-the output current changes of the electronic apparatus in relation to the variations in capacity in the sensitive devices in the input of said electronic apparatus forming a part of the Aapparatus of Figure 1.

Referring to the drawing, more particularly, reference character I designates a water drum of a boiler containing a liquid which may be water 2 normally at a level 3. 'Ihe drum I is provided with the usual gauge glass 4 connected to fittings 5 and 5a communicating with the drum above and below, respectively, the level 3.

The gauge glass 4 has mounted thereon an upper liquid level pick up clip 6 situated at the normal liquid level 3. This clip 6 is similar to the clip I2 shown and described in my copending application Ser. No. 479,917 filed Dec. 31, 1942, for Control apparatus, executedOct. 21, 1942,

` and acts as a pair of condenser plates forming a the plates of the clip and decreased by the receding of the liquid. This clip 6 is connected to a self contained grid tank unit 8 substantially the I with the hypothetical liquid level in the drum I which would be considered so dangerously low as to require shutting down of the fuel supply to the burner 2l hereinafter referred to.

This lower liquid level clip "I, also takes the form and functionfof a condenser having two plates and whose capacity is lowered when the water recedes between the said plates.

The unit 8 differs from the unit I4 of the aforesaid copending application onlyin that this second clip I is connected with its condenser in parallel with the condenser of clip 6 which is led to the opposite ends of the inductance in said unit 8, a pair of conductors 8b and 8c leading from said clip 'I to said opposite ends also.

The oscillating circuit of unit 8 is separably connected to a dual conductor cable I0 having 'a concentric conductor and vconducting sheath, said cable being 'separably connected to an oscillator, circuit 9, all of which unit 8, cable IIJ and oscillator 9 are substantially the same, with the differences herein noted, as shown and described in the aforesaid copending application.

The principal difference between the electronic oscillator circuit 9 and the oscillator circuit in said copending application is that the latter circuit has only one relay (58) in its output plate circuit whereas in the present casethere are two relays II and I2 respectively with their windings in series in the output plate circuit of the oscillator 9. These relays are chosen to pull up at widely different plate current levels. The characteristics, including the constants of the clips 6 and l and the windings of the relays II and I2, are so chosen and adjusted that when the liquid level is at normal level 3 in the drum I, the output plate current of the oscillator 9 will -be low and release the relay II to open contacts IIa and -deenergize an electric supply valve I3, feeding boiler drum. -When the liquid level recedes the reverse occurs'to energize and open said valve as in the aforesaid copending application to maintain the liquid level 3. This system takes care of normal liquid level control. A pilotA light I5 across valve I3 indicates to operator normal operation of control valve. Should the liquid level within drum I drop to and below the clip I as would be the case if there were a failure of liquid supply from source I 4 or failure of valve I3 to operate, the relay I2 will pull up because with the exception hereinafter noted. A similar lower liquid level clip 'I isv mounted on the glass 4 at a level corresponding alliance e l 3 it operates at a higher that of relay II. This dierent plate current level is caused by the further detuning of the oscillator circuit due to the impedance changes effected in the-oscillating circuit within the unit l by the further capacity decrease which takes.

place in the clip 1 when the liquid level is lowered to and below the latter. The relationship between thecapacities (with level changes) of the clips 6 and 1 and the resultant plate currents through the windings of the respective re- This is accomplished by connections wherein contacts I2a, operated by relay I2, are interposed in circuit with the Winding of a multi-contact third or controlY relay I1 and a normally closed push button 2l across the line supply I6,

Assuminglthat the contact I2a has been closed due to the pull up of the armature of relay I2 with a high plate current level coinciding to a level position below clip 1, current will flow from line supply through contact I2a to coil I1 whereupon armature I9 will pull up opening contact 22-2I to deenergize fuel supply valve 25 shutting down burner. Contact 2I-20 will be made causing the energizing of alarm 22 as a warning to the operating engineer. Contact I8-I8a will be closed so that any further change of contacting of I2a cannot disturb the locked up' position of relay I'I. The relay II is also pulled up with the high piste current level maintaining contact IIa closed and the water feeding control valve I3 open so that the boiler may be fed upon the resumptionof liquid -flow.

A normal closed push button 24, if depressed during the condition of liquid level -below clip 1 has no effect in resetting relay I'I, since the coil IIa remains energized through closed contact I2a and the alarm 23 continues to be energized.

Should the level be restored above clip l, oscilla-v tor approaches resonance as the capacity of clip 'I is increased, plate current falls, contact I2a opens and the operator may then depress push button 2t whereupon relay II now becomes deenergized restoring the valve 25 to open position to again supply fuel to the burner at the same time the alarm `23 is deenergized through opening of contact 2I-.2II. The apparatus is now restored for normal liquid level control around clip 6.

This control relay II has contacts 2l and 22 which `when closed and being in circuit with fuel valve 25 across the line during normal opening, of the relay I1 maintain the fuel supply on by holding said valve open.

A pilot light or alarm bell 23 is energized by the closing of relay contact 20 which connects said light (or bell) across the line when relay Il is energized. A contact I8 of relay I'I is closed by the energization of relay Il to maintain the same energized by directly connecting the relay winding across the line, independently of contact I2a, until push button 24 has been operated to reset said relay.

The burner 21 extends through the furnace plate current'level from` wall 29 to form a flame 28 for heating the boiler of which drum I is apart.

The advantages of the aforedescribed appara-l tus will be apparent without further detail.

. I am aware that many changes may be made and details varied without departing from the principles of my invention and I therefore do not wish to be limited to the detalls shown or described.

I claim:

1. In combination, a liquid container, .a'liquid supply therefor, heating means for the container, liquid level impedance change responsive means responding to liquid level changes to and from predetermined normal liquid level in the boiler,

a second liquid level impedance change responsive means responding to liquid level changes to and from a predetermined dangerously low liquid level in the container and electronic oscillator means operatively connected to both liquid level means having an electro-responsive device in its output circuit responsive to the 'iirst liquid level means for controlling the liquid supply in accordance with liquid level departures to and from normal level and having a second electroresponsive device in its output circuit responsive i to the second liquid level means for controlling the heating means.

the liquid supply in accordance with liquid level departures to and from normal level and having a second electro-responsive device in its output circuit responsive to the second liquid level means for controlling the heating means and a control means for the heating means so con-A nected between the second electro-responsive device and the heating means as to be operable by said second device only to shut off the heating means but not to restore same.

3. In combination, a container, a liquid supply therefor, heating means for container, liquid level impedance change responsive means responding to liquid level changes to and from pre-determined normal liquid level in the container, a second liquid level impedance change responsive means responding to liquid level changes to and from a predetermined dangerously low liquid level in the container and electronic oscillator means operatively connected to both liquid level means having an electro-responsive device in its output circuit responsive to the first liquid level departures to and from normal `level for controlling the normal level and having a second electro-responsive device in its output circuit responsive to the second liquid level means for controlling the heating means, and initiating means and control means so connected between the second electro-responsive device and the heating means that the control means is operable by said second device to shut off the heating means but is not operable to restore the heating means without first operating the initiating means.

- therefor, heating means for the container, liquid level impedance change responsive means responding to liquid level changes to and from a predetermined normal liquid level in the container, a second liquid level impedance change responsiv'e means responding to liquid level changes to and from a dangerously low liquid level in the container and an electronic oscillator controlled by both liquid level means and operatively connected to the liquid supply for automatically controlling the liquid level, and, also operatively connected to the heating means for shutting the same down when the liquid level approaches a dangerously low level;

5. In combination, a container,.a liquid supply therefor, heating means for the container, liquid level impedance change responsive means responding to liquid level changes to and from a predetermined normal liquid level in the 'containerl a second liquid level impedance change responsive means responding to liquid level changes to and from a dangerously low liquid level in the container, an electronic oscillator apparatus having a plurality of current levels in response to the respective liquid level means and.

relay apparatus iny the output circuit of said electronic apparatus responsive to the respective current level for controlling the normal level of the liquid in the container and for cutting the heating means off when. the liquid level approaches a dangerously low level.

6. In combination, a container, a liquid supply therefor, heating means for the container, liquid level impedance change responsive means responding to liquid level changes to and from vnormal liquid level in the container, a second liquid level means impedance change responsive to liquid level changes to and from a dangerously low liquid level in the container, an electronic oscillator apparatus controlled `by both liquid level means and operatively connected to the liquid supply for maintaining the liquid level and also operatively connected to the heating means for shutting the same oil when the liquid level approaches a dangerously low level, and control means interposed between the heating means and 'the electronic apparatus as to be operable thereby to shut off the heating means but not to restore same. l

7. In combination, a container, a liquid supply therefor, heating means for the container, liquid level impedance change responsive means responding-to liquid level changes to and from normal liquid level in the container, a second liquid level impedance change responsive means responsive to liquid level changes to and from a dangerously low liquid level in the container, an electronic oscillator apparatus controlled by both liquid level means and operatively connected to the liquid supply for maintaining the liquid level and also operatively connected to -the 'heating means for shutting the same off when the liquid level approaches a dangerously 10W level and initiating and control means interposed between the heating means and the electronic apparatus whereby the latter may operate the control means to shut off the heating means ybut operation of the initiating means is necessary to restore the heating means.

8. In combination, a container, a liquid supply therefor auxiliary control means, liquid level impedance change responsive means responding to liquid level changes to and from a predetermined normal liquid level in the container,'a second liquid level impedance change-responsive means responding to liquid level changes to and from a 9. In combination, a container, a liquid supply therefor, heating means for the container, liquid level impedance change responsive apparatus having a plurality of operating ranges, one range responding to liquid level changes to and from a predetermined normal liquid level in the container and the other range responding to liquid level changes to and from a dangerously low level in the container and electronic oscillator means controlled by both ranges and operatively connectedto the liquid supply yfor automatically controlling the liquid leveleand also operatively connected to the heating means for shutting the same down when the liquid level approaches a dangerously low level. I

10. In combinatioma container, a liquid supply therefor, burner control i means, a manometer associated with the container, capacitor plate pickups responding to liquid level changes to and from a-predetermined normal liquid level in the manometer, a second set of capacitor plate pickups responding to liquid level changes to and from a dangerously low liquid level in the' manometer and an electronic oscillator apparatus controlled by both sets of capacitor plate pickups and operatively connected to the liquid supply for automatically controlling liquid level at a normal level and also operatively connected to the burner control means for controlling the same when the liquid level approaches a dangerously low level. ll. The combination of a container, a/liquid supply therefor, heating means for the container,

, liquid level responsive apparatus, responding to liquid level changes to and from a predetermined normal liquid level in the container, an oscillator circuit spaced a substantial distance from the container, an oscillating circuit mechanically mounted in proximity to said liquid level responsive apparatus and operatively connected thereto for control thereby, ay concentric conductor cable eratively connected to said heating means for controlling the same'in accordance with the second liquid level responsive apparatus.

THEODORE A. COHEN. 

